This application claims the benefit of Italian National Patent Application Serial No. TO2001A000597 filed on Jun. 20, 2001, naming the same inventors as identified herein, which is hereby incorporated by reference in its entirety.
The present invention relates to a pump for liquids and, in particular, to a centrifugal pump for electric household appliances and the like, for example, of the type to be operated by an alternating-current electric motor such as, in particular, a synchronous electric motor having a rotor with permanent magnets.
An object of the present invention is to propose an improved pump in which the hydraulic isolation between the rotor chamber and the environment in which its electric drive motor is disposed is ensured for as long as possible.
A further object of the invention is to propose a pump for liquids which is highly reliable and very quiet in operation.
This and other objects are achieved, according to the invention, by a pump for liquids comprising:
a rigid support structure including a body having an annular end in which an opening is defined, and a volute connected to the said end of the body so as to define a pumping chamber therewith,
a bladed rotor disposed in the chamber and connected to a drive shaft which is mounted rotatably in the body and extends through the opening, a first annular sealing member and a second annular sealing member which are carried by the structure and encircle the drive shaft in a leaktight manner in respective axially spaced-apart positions,
a lubrication chamber containing a lubricating grease being defined between the sealing members and the drive shaft, and
a first sealing ring, closer to the rotor, having a radially inner portion which forms at least one sealing lip which bears on the shaft, and a radially intermediate circular portion which is disposed outside the at least one lip and has a substantially U-shaped cross-section with its convex side facing the rotor.
By virtue of these characteristics of the first annular sealing member, the volume of the lubrication chamber is advantageously maximized and the quantity of grease which can be provided therein in correspondingly maximized. This ensures effective lubrication and optimal hydraulic isolation of the pumping chamber, in particular against any possible escapes of liquid by leakage along the rotor drive shaft.
According to a further characteristic, a shaped disc is disposed between the rotor and the first sealing ring and has a central opening through which the drive shaft extends with radial clearance; on the side facing the rotor, this disc has at least one annular projection which at least partially axially penetrates a corresponding annular element of the rotor in order to define a labyrinthine radial path therewith. The convex side of the radially intermediate circular portion of the first sealing ring, thus, advantageously extends in the immediate vicinity of (or even in contact with) the portion of the shaped disc which surrounds the drive shaft.
By virtue of this characteristic, the annular volume defined around the drive shaft between the first sealing ring and the shaped disc is thus minimized. The creation of any turbulence phenomena or vortices in this space is correspondingly reduced, with beneficial effects on the smoothness of rotation of the rotor and on the reduction of operating noise.